This invention relates to improved equipment and methods for making continuous fastener products and the like, and to products produced by the equipment and methods.
Fastener products, such as hook components of hook-and-loop fasteners, are manufactured by a continuous molding method employing a cylindrical mold roll which has fastener-shaped cavities formed in its periphery. Often the mold roll is formed of an axially compressed stack of ring-form mold plates. In operation, molten polymer from an extruder is introduced into a pressure zone in which the molten polymer is forced under high pressure into the fastener cavities of the cooled mold roll, to form fastener elements (e.g. hooks) integrally molded with a base layer. In some cases the pressure zone is a nip formed by a mold roll and an adjacent pressure roll. In other configurations the pressure zone is formed between a conforming stationary pressure head and a mold roll. Typically, the smaller the fastener elements (or the like), the faster the optimal production speed. The more viscous the resin, or the lower the temperature of the cooled roll, the higher must be the pressure achieved in the pressure zone in order to make a satisfactory product. Typically, mold rolls of about 10 inch diameter and 12 inches in axial length have been employed.
We have realized that many advantages can be obtained by employing longer mold rolls and correspondingly wide pressure zones to form wide products, while providing means to accommodate effects of the distribution of pressure along the length of the mold roll. By this means, products molded with wide widths can have uniform product thickness and other properties previously found only in narrower materials.
We also have realized that many advantages can be obtained by raising the pressure in the pressure zone, with a conventional roll or a longer roll, to form products having finer features while providing means to accommodate effects of the distribution of pressure along the length of the mold roll.
We have realized that, because of the construction of the molding region of the mold roll as a stacked series of rings or plates about a central shaft, the mold roll has limited bending resistance. As a result, if the molding region of the mold roll is made long to produce a wide product, or if the pressure of the resin is increased, the tendency of the mold roll to bend away from the pressure zone under the extreme molding pressure can cause small separations between adjacent mold plates and undesirable base layer thickness variation across the width of the product (i.e. gap variation along the length of the molding region). Also, we realize that non-uniform geometry of the pressure zone can produce detrimental nonuniformity in the pressure distribution across the pressure zone, which can lead to incomplete filling of some of the mold cavities.
According to one aspect of the invention, improvements are made in an apparatus for continuously molding fastener elements integral with a base web from a flowable resin. The apparatus comprises a cylindrical mold roll rotatable about an axis and defining small fastener element-shaped mold cavities in the surface thereof, and pressure-applying means to apply elevated operating pressure to force the resin into the cavities at a pressure zone. The pressure-applying means and mold roll define a mold gap therebetween for forming the base web. The provided improvements include means to maintain the mold gap at a desired thickness profile across the length of the molding region under operating pressure that would otherwise tend to produce gap variations.
The provided improvements are particularly useful if the molding region of the mold roll is lengthened to about 12 inches or more or if the operating pressure is raised to higher levels, such that the mold roll is subject to loads in the range of about 1000 to 1600 pounds per lineal inch along the mold roll.
In a preferred configuration, the mold roll comprises an axially arranged stack of a large multiplicity of disks, at least many of which have mold cavities at their peripheral surfaces.
In certain advantageous embodiments, the means to maintain the mold gap comprises a moving support member on the side of the mold roll generally opposite the pressure-applying means. The support member is disposed to engage the peripheral surface of the mold roll with sufficient force to resist radial deflection of the mold roll. Preferably a support member controller is provided to vary the amount of engagement between the mold roll and the support member in response to operating conditions.
In certain embodiments, the apparatus includes a sensor to provide operating condition information to a support member controller. In some cases the sensor is constructed to detect the presence of molded resin on the peripheral surface of the mold roll and the controller is constructed to disengage the support member from the peripheral surface of the mold roll when resin is not present. In certain arrangements, the sensor is constructed to respond to a condition of the apparatus that is related to the pressure in the pressure zone.
In some preferred embodiments of the invention the depth of the mold cavities from the surface is between about 0.004 and 0.035 inches, preferably between about 0.005 and 0.020 inches, and more preferably between about 0.006 and 0.012 inches.
Broadly, the invention relates to completed fastener elements and to components or preforms that form a part of, or are modified to form, a completed fastener. The term xe2x80x9cfastener elementxe2x80x9d as used herein is intended to include all of these forms.
In some embodiments, however, the mold cavities preferably define the shape of functional fastener elements. In some preferred arrangements the mold cavities at least partially define the shape of loop or fiber-engaging hook elements, each element having a pedestal or stem portion and at least one head portion that projects to a side of the pedestal or stem portion. In other arrangements, the fastener elements are of mushroom shape or of stem-shaped preforms that are subsequently processed to form mushrooms or other elements having flat or rounded heads.
In some particularly useful embodiments, the support member that engages the mold roll has a peripheral surface that is resiliently deformable to conform, in the vicinity of its engagement with the mold roll, generally to the peripheral surface of the mold roll. In some of these instances, the portion of the support member that directly contacts the surface of the mold roll is of a resilient substance, preferably an elastomeric material.
In some preferred embodiments the support member comprises a generally cylindrical roll arranged to rotate about an axis of rotation, while in some other embodiments the support member comprises a belt supported to engage the mold roll with substantial pressure.
In some embodiments the means to maintain the mold gap comprises adjustable structure to elastically deform the shape of the pressure-applying means, to conform to axial deflection of the mold roll. In some cases, the pressure-applying means comprises a pressure roll, the mold gap comprises a nip between the mold roll and pressure roll, and the means to elastically deform the shape is constructed to bend the axis of the pressure roll to maintain the mold gap. In some other cases, the pressure-applying means comprises a nozzle assembly for introducing the resin to the pressure zone under pressure, the mold gap comprises a gap between this nozzle assembly and the mold roll, and the means to elastically deform the shape is constructed to bend the nozzle assembly along the length of the mold gap to maintain the mold gap.
In some preferred embodiments the pressure-applying means comprises a pressure roll rotatable about an axis and positioned to form a nip with the mold roll to provide the mold gap. The means to maintain the mold gap includes a controller to vary the angle between the axes of the pressure and mold rolls to introduce skew to compensate for mold roll deflection under operating pressure.
In various arrangements according to the invention, means are provided to extract heat from the surface of the support member to cool the support member, thus to withdraw heat from the molding process.
According to another aspect of the invention, an apparatus is provided for continuously molding two streams of fastener product from flowable resin, each product comprising a base web with integral fastener elements. The apparatus has a cylindrical mold roll rotatable about an axis and defining small fastener element-shaped mold cavities in its surface in a molding region. The apparatus also has first and second pressure-applying means to apply operating pressure to force the resin into the cavities of the mold roll at corresponding first and second pressure zones. The first and second pressure-applying means and the mold roll define corresponding first and second mold gaps therebetween for forming the base webs in the molding region. First and second product-removing means are included to remove the product from the mold roll. The first and second pressure-applying means are advantageously arranged on generally opposite sides of the mold roll, such that bending loads applied to the mold roll by the elevated operating pressures of the two pressure applying means are substantially balanced. Preferably, the mold roll is of extended length of about 12 inches or more to produce correspondingly wide webs.
In some embodiments the first and second pressure-applying means each comprises a pressure roll and the first and second mold gaps each comprises a nip between the mold roll and a corresponding pressure roll.
In some other embodiments, the first and second pressure-applying means each comprises a nozzle and shoe assembly for introducing the resin to the corresponding pressure zone under pressure and the first and second mold gaps each comprises a gap between a corresponding nozzle assembly and the mold roll.
According to another aspect of the invention, an apparatus, for continuously molding small fastener elements integral with a base web from a flowable resin, has a cylindrical mold roll rotatable about an axis and defining fastener element-shaped mold cavities at its surface in a molding region, and pressure-applying means are arranged to apply operating pressure to force the resin into the cavities at a pressure zone. The pressure-applying means and mold roll define a mold gap therebetween for forming the base web in the molding region. The apparatus includes a roll arranged to engage the mold roll with substantial force, and which has a resiliently deformable surface to conform, in the vicinity of its engagement with the mold roll, generally to the peripheral surface of the mold roll along the molding region.
In some embodiments, the molding region of the mold roll is of about 12 inches or more in length and the resiliently deformable roll comprises a pressure roll positioned to form a wide nip with the mold roll to provide the mold gap, to form a correspondingly wide web. In these and other embodiments, preferably a substantially elevated pressure is maintained in the pressure zone to produce a load of between about 1000 and 1600 pounds per lineal inch against the mold roll in the molding region.
In some embodiments, the resiliently deformable roll comprises a support roll disposed to engage the mold roll on the side generally opposite the pressure-applying means to resist deflection of the mold roll.
In some embodiments useful for producing a laminated fastener product comprising a molded web and a backing material, the resilient roll and the mold roll define therebetween a laminating zone for laminating the molded web to the backing material.
According to another aspect of the invention, an apparatus for continuously molding fastener elements integral with a base web from a flowable resin has a cylindrical mold roll rotatable about an axis and defining fastener element-shaped mold cavities at a surface thereof, pressure-applying means to apply operating pressure to force the resin into the cavities at a pressure zone (the pressure-applying means and mold roll defining a mold gap therebetween for forming the base web), and a belt arranged to engage the mold roll.
In some embodiments the belt is arranged to engage the mold roll on the side generally opposite the pressure-applying means to resist radial deflection of the mold roll.
In some embodiments the belt and the mold roll define a laminating zone therebetween for laminating the molded web to a backing material.
In some cases, the belt is constructed to extract heat from the surface with which it is engaged.
According to another aspect of the invention, certain other improvements are provided in an apparatus for continuously molding fastener elements integral with a base web. The apparatus has a cylindrical mold roll rotatable about an axis and defining fastener element-shaped mold cavities in the peripheral surface thereof, and a nozzle assembly to introduce a flowable resin to the cavities. The nozzle assembly is constructed and arranged to apply operating pressure to force the resin into the cavities at a pressure zone, and the nozzle assembly and mold roll define a mold gap therebetween for forming the base web, the apparatus including means to maintain the mold gap at a desired thickness profile across the width of the wide web under the operating pressure if the roll is lengthened or if the operating pressure is raised to higher levels such that the mold roll is subject to loads in the range of about 1000 to 1600 pounds per lineal inch along the mold roll.
In some embodiments the means to maintain the mold gap comprises a support member disposed to engage the mold roll on the side generally opposite the nozzle assembly with sufficient force to resist radial deflection of the mold roll, and a controller constructed to vary the amount of engagement between the support member and the mold roll. In some cases the support member is resiliently deformable.
In some embodiments the means to maintain the mold gap comprises an actuator to elastically bend the nozzle assembly to conform to radial deflections of the mold roll to maintain the mold gap, and a controller constructed to control the actuator to vary the amount of bending of the nozzle assembly.
According to another aspect of the invention, an apparatus for continuously molding fastener elements integral with a base web includes a cylindrical mold roll, preferably of extended length to provide a correspondingly wide web, and a cylindrical pressure roll. The mold roll is rotatable about an axis and comprises multiple stacked disks having fastener element-shaped mold cavities in their peripheral surfaces. The cylindrical pressure roll is arranged to engage the mold roll at a nip to form a mold gap for forming the base web. The pressure roll is constructed to apply operating pressure to force the resin into the cavities. The apparatus also includes an extrusion die to introduce a flowable resin to the nip, and means to maintain the mold gap at a desired thickness profile across the width of the wide web under the operating pressure, preferably a substantially elevated pressure.
In some embodiments the means to maintain the mold gap comprises a support roll arranged to engage the mold roll on the side generally opposite the nozzle assembly with sufficient force to resist radial deflection of the mold roll, and a controller constructed to control the amount of engagement between the support roll and the mold roll in response to operating conditions.
In some embodiments the means to maintain the mold gap includes a controller to vary the angle between the axes of the pressure and mold rolls to introduce skew to compensate for mold roll radial deflection under operating pressure.
By xe2x80x9cradial deflectionxe2x80x9d as used herein, we mean any lateral deflection of any portion of the axis of the roll, including bending or bowing deflections.
According to another aspect of the invention, an apparatus for continuously molding fastener elements integral with a base web includes a cylindrical mold hoop rotatable about an axis and having fastener element-shaped mold cavities in its peripheral surface. The apparatus also has at least one driven roll arranged to engage an inner surface of the mold hoop to drive the hoop and a pressure-applying means arranged to apply operating pressure to force the resin into said cavities at a pressure zone.
In some embodiments of the apparatus of the invention, the pressure-applying means is constructed to apply first and second operating pressures at corresponding first and second said pressure zones at first and second mold gaps, respectively, with the mold roll. In some instances, the pressure-applying means comprises a nozzle assembly for introducing resin to the first pressure zone at the first operating pressure, the first mold gap comprising a gap between the nozzle assembly and the mold roll. In some cases, the pressure-applying means also includes a pressure roll, the second mold gap comprising a nip between the mold roll and pressure roll.
According to another aspect of the invention, a method of continuously molding fastener elements on one broad side of a sheet product opposite another broad side having surface features, e.g., raised or indented portions, is provided. The method comprises providing an apparatus that includes a mold roll, resiliently deformable pressure roll, and an extruder die, all as described above, passing a sheet product having the surface features through the nip with the molten resin such that the resilient surface of the pressure roll conforms in the vicinity of the features to protect the features as they pass through the nip. The method also includes forming fastener elements integral with a base web on a broad side of the sheet product.
In some embodiments, an abrasive sheet product having molded fastener elements on one side and abrasive particles on the other side is formed by the in situ laminating method just described, in which the surface features comprise abrasive particles.
In some embodiments the surface features comprise a decorative texture such as an enclosed pattern or decorative fibers as in grass cloth. In some embodiments, the sheet product comprises a wall covering covered on its back side with fastener elements.
Various aspects of the invention disclosed here enable cost-effective commercialization of molded fastener products of extremely wide widths and products having many very small fastener elements. In particular, fastener products with very thin base layer thicknesses held to very close dimensional tolerances can be produced in a practical manner. According to another aspect of the invention, the contact from loading systems that are provided according to the invention in the form of load rolls or load belts, are advantageously employed to extract heat from the back of the base layer of the product, to enable production of thicker base layers or to produce a product with a given base thickness at a much higher production speed than has previously been possible.
As will be understood from the foregoing and the remaining description and drawings, various features of the different aspects of the invention may be advantageously combined in other embodiments for certain applications.